1. Field of the Invention
The present invention relates to telecommunications and more particularly to digital broadcast television.
2. Description of the Related Art
In the U.S, a broadcast license is a specific type of spectrum license that grants the licensee the privilege of using a portion of the radio frequency spectrum in a given geographical area for broadcasting purposes. The determination of which frequencies can be used by various licensees is done through a frequency allocation process, which in the U.S., is specified by the Federal Communications Commission (FCC). The radio frequency spectrum can be divided differently, depending on for what it will be used. For instance, broadcasting for TV channels 21-36 can be allocated between 512 MHz and 608 MHz, while radiolocation, metrological aids, and maritime radionavigation can be allocated between 5.6 GHz and 5.65 GHz. Of note, the FCC regulates access to the spectrum for private, state, and local governmental uses, but the National Telecommunications and Information Administration under the Commerce Department allocates spectrum use by the federal government, including the military.
In order to receive a broadcast license, an applicant must file with the FCC, which decides whether to grant or deny the application. The exact process is different for public radio and public television, for community radio and community television, and for commercial applicants and licensees. Of note, in some cases (e.g., CB radio), the public may use the spectrum without the need of a license. A broadcast license typically specifies the following information: geographic coordinates, carrier frequency, bandwidth, modulation type, effective radiated power, height above average terrain, and directional antenna radiation pattern.
Once a license is granted, a transmission can be broadcasted. The broadcasting of television initially involves the analog transmission of broadcasting encoded analog audio and video signals. Broadcasters using analog television systems encode their signal using analog encoding and then modulate the encoded signal onto a very high frequency (VHF) or ultra high frequency (UHF) carrier. The analog television signal contains timing and synchronization information so that the receiver can reconstruct a two-dimensional moving image from a one-dimensional time-varying signal. The television system for each country will specify the number of television channels within the UHF or VHF frequency ranges. Of note, a channel actually consists of two signals: the picture information is transmitted using amplitude modulation on one frequency, and the sound is transmitted with frequency modulation at a frequency with a fixed offset (typically four and one-half to six megahertz) from the picture signal.
In the United States, full-power over-the-air broadcasts transitioned from analog broadcasts to digital television (DTV) in June 2009. Of note, in addition to full-power stations, there are also three other categories of TV stations in the U.S.: low-power broadcasting stations, Class A stations, and TV translator stations. Of further note, the digital broadcast television industry uses the Advanced Television Systems Committee (ATSC) standards for digital television transmission. Today delivery of video is accomplished using one transmitter, one antenna, and one frequency in an omni-directional, over-the-air, three hundred sixty degree radius in a given coverage area in conjunction with a single broadcast license, which allows up to 19.39 Mbps of data per broadcast television license to be broadcasted.